The present invention relates to a reproducing apparatus for reproducing information data from a disk-like recording medium, e.g., CD-ROM, a phase-change type optical disk and a magneto-optical disk and, particularly to a reproducing apparatus for transferring information data reproduced from a disk-like recording medium to an external device, e.g., host computer after the information data was temporarily stored therein.
Recently, use of auxiliary storage that can handle mass-storage data becomes indispensable for data processing using computers. In particular, in data processing for processing image data, music data and dictionary data, auxiliary storages are used in computer operation based on GUI (graphical user interface) where previously-determined background image, icon image or character image is displayed on a monitor, computer games, dictionaries and electronic books that can be substantially used as dictionaries.
Read-only optical disks (CD-ROMs) that can record mass-storage data become widespread because image data needs vehemently large capacity of data.
Semiconductor memories are generally assembled into an optical disk reproducing apparatus in order to efficiently transfer data recorded on an optical disk to a host computer. The reason for this is that a data transfer rate can be improved by temporarily storing data from the optical disk in the semiconductor memories.
Data can be stored temporarily even when data is stored in the semiconductor memory in response to a data read request command issued from the host computer to the optical disk. Because, if data except the data stored in the semiconductor memory is to be read out next, i.e., read address on the optical disk is different, data that had been stored in the semiconductor memory is erased and designated data newly read out from the optical disk is stored in the semiconductor memory.
When data is read out from the optical disk, data of a certain address is read out frequently or data of arbitrary address is read out randomly. In such a case, it is customary that the reproducing apparatus stores temporarily data read out from the optical disk in the semiconductor memory and transfers the data temporarily stored in the semiconductor memory to the host computer. Therefore, if data of random address on the optical disk is read out and transferred to the host computer after data has been read out from the address from which data is highly frequently and transferred to the host computer, then the former data is recorded on almost all portion of the semiconductor memory. As a consequence, when data of the address from which data is read out highly frequently is read out one more time, data of the address from which data is read out highly frequently should be read out from the optical disk from the beginning.
Data access time in the reproducing apparatus depends upon an average access time of the reproducing apparatus. Therefore, advantages of the semiconductor memory that is assembled into the reproducing apparatus in order to improve a data transfer rate cannot be demonstrated sufficiently.